An organic thin film transistor (OTFT) is made of organic conjugated polymer or oligoanolone. Compared with a conventional non-organic transistor, the OTFT can be constructed at a lower temperature, and thus the substrate of the OTFT can be a plastic substrate which is lighter, thinner and cheaper than the glass substrate of the conventional non-organic transistor. In addition, the organic thin film transistor can employ a simpler manufacture process that doesn't require certain high precision technique and equipment. In this regard, the OTFT are of great potential and interest for further development. Although the organic thin film transistor has the advantages as described above, there are still some bottlenecks choking the further research, such as low carrier mobility and high driving voltage. The low carrier mobility limits the development and application of OTFT. In general, as the active layer is made of crystalline silicon whose the orientation of each molecular is not the same, a boundary is formed between two different crystal systems and thus obstructs the movement of carriers so that to the performance of element is reduced. The research of OTFT focuses on how to form an active layer with organic semiconductor molecules of single crystal or large crystal. The method frequently used is to perform a surface treatment on the deposited organic semiconductor molecule. That is, an interlayer compatible to the crystal of organic semiconductor molecule is coated on the dielectric layer so as to improve the crystallization of the organic semiconductor molecular.
U.S. Pat. No. 6,433,359 discloses a method using a self-assembled monolayer (SAM) as the interlayer between organic semiconductor and dielectric layer. This method can make pattern in the interlayer only when the precursor can react with the dielectric layer. In this regard, the material of U.S. Pat. No. 6,433,359 has a limited choice, and the condition of the precursor reacting with the dielectric layer is not easily controlled. In addition, evaporation deposition is used for forming the interlayer of the U.S. Pat. No. 6,433,359 that the SAM is easily evaporated during the manufacturing process causing the same to have unstable quality.
Form the above description, the conventional process of OTFT has the following drawbacks:                1. The forming of interlayer in the conventional process of OTFT is complicated and time-consuming that the high manufacture cost of the conventional process is increased so as to reduce it commercial competitiveness.        2. The interlayer can be formed only when the precursor can react with the dielectric layer in the conventional process of OTFT, therefore the material of the interlayer has a limited choice, and the condition of the precursor reacting with the dielectric layer is not easily controlled.        3. The interlayer is formed by evaporation deposition so that the SAM is easily evaporated during the manufacturing process causing the same to have unstable quality.        